glib-2.0: Use g_abort for GLib.Process.abort() beginning with 2.50
glib-2.0: Use g_abort for GLib.Process.abort() beginning with 2.50

Fixes https://gitlab.gnome.org/GNOME/vala/issues/1350

GNOME/vala,frida/vala,frida/vala,GNOME/vala,frida/vala,frida/vala,frida/vala,GNOME/vala,GNOME/vala